The present disclosure relates to an exposure device and an image formation apparatus.
In related art, an image formation apparatus such as a printer, a photocopier, a facsimile, and a multi-function printer, for example an electrophotographic printer is provided with an image formation unit. The image formation unit is provided with a photosensitive drum, a charge roller, a development roller, and the like. An LED head as an exposure device exposes to light a surface of the photosensitive drum uniformly charged by the charge roller thereby to form an electrostatic latent image. The electrostatic latent image is developed with toner supplied from a toner cartridge, thereby forming a toner image. The toner image is transferred by a transfer roller onto a sheet and is fused by a fuser. In this way, an image is formed.
The LED head includes, for example: an LED array including LEDs; a substrate mounted with the LED array; a holder which holds the substrate; a rod lens array which is installed to the holder while facing the LED array, which converges light emitted from the LEDs of the LED array, and which produces an image at an image producing position on the surface of the photosensitive drum; and a base which keeps the substrate in contact with a contact surface of the holder.
When the LED array is driven, light is emitted from each of the LEDs. The rod lens array converges the emitted light and produces an image at the image producing position on the surface of the photosensitive drum, thereby exposing the surface of the photosensitive drum to light. As a result, an electrostatic latent image is formed (for example, Patent Document 1: Japanese Patent No. 4450848).
Here, in the printer described above, it is necessary to precisely position the substrate relative to the holder in order to precisely expose the surface of the photosensitive drum to light.
To this end, the holder is manufactured using die cast aluminum. The contact surface of the holder to be brought into contact with the substrate is machined to have a flatness of about 20 [μm].